MCC iPort/USB 2, Руководство пользователя

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3.3 Connecting to an SMBus Target System
If you are connecting the I
2
C adapter to a SMBus target system, you should follow
these steps BEFORE applying power:
• Shut off the iPort/USB 2 internal pull-ups (See Pull-up Resistor section).
• Use external SMBus rated (appoximately15k ohms) pull-up resistors. These
pull-ups may already be present in the target system.
• Visit our I
2
C versus SMBus FAQ page (www.mcc-us.com/I2CSMBusFAQ.htm).
• See the SMBus Specification for additional details.
Special Note for SMBus Users : MCC’s I
2
C adapters are designed to be I
2
C Bus
compatible, not SMBus compatible. Some features of the SMBus protocol not
supported include time-outs, device reset, and Packet Error Check byte processing.
The non-supported SMBus features may, or may not, permit the use of the I
2
C
adapter in your SMBus application. Consult the MCC FAQ web page and SMBus
Specification for details.
4 ESD (Electrostatic Discharge) Precautions
Zap! Everyone is familiar with walking across a rug and getting zapped when
touching a metal object. But how can that zap damage electronics.
Electrostatic discharge is defined as the transfer of charge between bodies at
different electrical potentials. Electrostatic discharge can change the electrical
characteristics of a semiconductor device, degrading or destroying it. Electrostatic
discharge also may upset the normal operation of an electronic system, causing
equipment malfunction or failure.
When connecting the I
2
C adapter to a host computer and a target system, extreme
care must be taken to avoid electrostatic discharge. Failure to follow ESD protection
procedures when using the I
2
C adapter could damage the host computer, I
2
C
adapter, or the target system, and void product warranty coverage.
4.1 Host Computer Grounding
Case 1 - Desktop and Single-board Computers. The chassis on a desktop or
single-board host computer must be connected to earth ground to comply with
safety regulations. If the computer chassis is NOT connected to earth ground for